#include<iostream>
#include<string>
#include<vector>
using namespace std;
string a, b, ans;
vector<int> sub(vector<int> A, vector<int>B)
{
	vector<int>ans;
	int t = 0;
	for (int i = 0; i < A.size(); i++) {
		t = A[i] - t;
		if (i < B.size()) {
			t -= B[i];
		}
		ans.push_back((t + 10) % 10);
		if (t >= 0) {
			t = 0;
		}
		else {
			t = 1;
		}
	}
	while (ans.size() > 1 && ans.back() == 0) {
		ans.pop_back();
	}
	return ans;
}
int main()
{
	cin >> a >> b;
	vector<int>A, B, SUB;
	for (int i = a.size() - 1; i >= 0; i--) {
		A.push_back(a[i] - '0');
	}
	for (int i = b.size() - 1; i >= 0; i--) {
		B.push_back(b[i] - '0');
	}
	SUB = sub(A, B);
	for (int i = SUB.size() - 1; i >= 0; i--) {
		cout << SUB[i];
	}
	cout << endl;
	return 0;
}